The invention relates to an image transfer unit for use in an electrophotographic copying machine which incorporates a transfer roller to which a bias voltage is applied.
An image transfer unit of the kind described is confronted with the problem of smearing of the back side of the transfer sheets that results from the deposition on the surface of the transfer roller of a toner, which is floating in the internal space of the copying machine or which is driven from non-image areas on a photosensitive member. The deposited toner contaminates the back surface of the transfer sheet which is held between the photosensitive member and the transfer roller during the image transfer step. Therefore, it is necessary to provide some cleaning unit for removing toner which is deposited on the transfer roller in order to prevent a smearing of the back side of the transfer sheet.
Conventional means for cleaning the transfer roller comprises a blade which is brought into abutting relationship therewith to scrape any toner therefrom, or comprises a rotatable brush which is urged against the transfer roller to wipe off any toner thereon. These arrangements require some form of toner processing means which collects the separated toner or which prevents redeposition of the separated toner onto the transfer roller.